Ab initio ballistic conductance with spin-orbit coupling: Application to monoatomic wires

The approach proposed by Choi and Ihm [Phys. Rev. B 59, 2267 (1999)] for calculating the ballistic conductance of open quantum systems within the Landauer-Buttiker approach is generalized to fully relativistic ultrasoft pseudopotentials, enabling it to deal with ballistic transport in the presence of spin-orbit coupling. As a test case, we present the complex k-vector electronic structure of a perfect monoatomic nonmagnetic Pt wire, and the ballistic conductance of a toy nanocontact model consisting of the same Pt nanowire with one stretched bond. By comparing the fully relativistic and the scalar relativistic results, it is seen that the relative importance of spin-orbit effects can be quite large.